Cytochrome c‐d regulates developmental apoptosis in the Drosophila retina

Abstract

The role of cytochrome c (Cyt c) in caspase activation has largely been established from mammalian cell‐culture studies, but much remains to be learned about its physiological relevance in situ. The role of Cyt c in invertebrates has been subject to considerable controversy. The Drosophila genome contains distinct cyt c genes: cyt c‐p and cyt c‐d. Loss of cyt c‐p function causes embryonic lethality owing to a requirement of the gene for mitochondrial respiration. By contrast, cyt c‐d mutants are viable but male sterile. Here, we show that cyt c‐d regulates developmental apoptosis in the pupal eye. cyt c‐d mutant retinas show a profound delay in the apoptosis of superfluous interommatidial cells and perimeter ommatidial cells. Furthermore, there is no apoptosis in mutant retinal tissues for the Drosophila homologues of apoptotic protease‐activating factor 1 (Ark) and caspase 9 (Dronc). In addition, we found that cyt c‐d—as with ark and dronc—regulates scutellar bristle number, which is known to depend on caspase activity. Collectively, our results indicate a role of Cyt c in caspase regulation of Drosophila somatic cells.

Tousled-like kinase mediated a new type of cell death pathway in Drosophila

“…When raised at 25°C, each ommatidium adopts a rigid hexagonal pattern in the wild-type flies at 40 h APF (after pupa formation), and anti-Armadillo staining can visualize each cell in the developing retina. 32 To quantify the number of IOCs in the developing retina, a hexagonal target area is defined by connecting the center of six ommatidia surrounding a central ommatidium (Figure 2A a). 33 GMR>white …”

“…At least 30 hexagonal target areas were scored from three to six different flies for each experiment as reported by others. 32 …”

Living with death: the evolution of the mitochondrial pathway of apoptosis in animals

“…In one study, silencing expression of either or both Drosophila cytochrome c proteins was found not to affect apoptosis in the fly, and addition of either recombinant forms of these proteins or whole mitochondrial extracts to cell-free systems failed to significantly activate caspases in Drosophila cell lysates, although addition of recombinant Drosophila cytochrome c does yield caspase activation in mammalian lysates. [42][43][44] However, studies on flies lacking d-cyt-c, one of the Drosophila cytochrome c genes, found severely delayed apoptosis in the developing retina, 45 and a genetic screen found that mutations in d-cyt-c reduced caspase activation during spermatid individualization, 46 an effect phenocopied by ARK or DRONC loss-offunction mutations. An earlier study found that an otherwise hidden epitope of cytochrome c is presented early in the Drosophila apoptotic program, although this putative conformational change is apparently caspase dependent and proceeds without release of cytochrome c from the mitochondria.…”

Cell death: what can we learn from flies? Editorial for the special review issue on Drosophila apoptosis

“…There is mounting evidence to challenge this view: (1) the Drosophila Bax/Bak ortholog debcl is required for some developmental apoptosis [28], (2) developmental apoptosis in the retina and non-apoptotic activation of caspase require Cyt-c [29][30][31] and (3) active apoptosome complexes are constantly subjected to feedback inhibition in living cells [20]. This suggests that activation of the apoptosome is not constitutive and that the apoptosome is activated by a signal (Cyt-c or another factor) in dying cells.…”